1. Field of the Invention
This invention relates to robotic semiconductor wafer transfer system used in the moving of semiconductor wafers between a wafer cassette to a wafer boat within a vertical furnace and more particularly and guards and shields to protect components of the semiconductor wafer transfer system during preventive maintenance procedures.
2. Description of Related Art
Referring to FIG. 1, a robotic wafer transfer system 5, similar to that described in U.S. Pat. No. 5,380,137 (Wada), will pick wafers W from a wafer cassette 15 and place them in a wafer boat 20. The wafer boat 20 is housed within a vertical oven (not shown). The vertical oven will be sealed and a step of the semiconductor process such as chemical vapor deposition will be performed on the semiconductor wafers. At the completion of the step of the process involving the vertical oven, the wafers W are removed from the wafer boat 20 and returned to the wafer cassette 15.
The semiconductor wafers W are supported on the semiconductor wafer carrier forks 10. These semiconductor wafer carrier forks 10 are manufactured of a ceramic and contain an electro-optical sensor. The design of the semiconductor wafer carrier forks 10 coupled with the electro-optical form a unit that is extremely fragile.
Preventive maintenance to repair or replace components of the vertical oven and robotic wafer transfer system and other machinery involved in the semiconductor process requires the disassembly of the subunits of the these systems. As the subunits are disassembled, parts such as screws, nuts, or bolts may dropped. If the work area is above the wafer carrier forks 10, they may be broken or damaged necessitating replacement.
U.S. Pat. No. 4,785,962 (Toshima) describes a slit valve for sealing a vacuum chamber within the semiconductor wafer process and shows a robotic transfer system for conveying semiconductor wafer to the vacuum chamber.